Buggy code:
public abstract class MarkupContainer < T > extends Component < T > { private static final long serialVersionUID = 1L ; private static final Log log = LogFactory . getLog ( MarkupContainer . class ) ; private Object children ; private transient MarkupStream markupStream ; MarkupContainer ( ) { } public MarkupContainer ( MarkupContainer parent , final String id ) { } public MarkupContainer ( MarkupContainer parent , final String id , IModel < T > model ) { } final MarkupContainer add ( final Component < ? > child ) { if ( child == null ) { throw new IllegalArgumentException ( "argument<seq2seq4repair_space>child<seq2seq4repair_space>may<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null" ) ; } if ( MarkupContainer . log . isDebugEnabled ( ) ) { <START_BUG> MarkupContainer . log . debug ( ( ( ( "Add<seq2seq4repair_space>" + ( child . getId ( ) ) ) + "<seq2seq4repair_space>to<seq2seq4repair_space>" ) + ( this ) ) ) ; <END_BUG> } addedComponent ( child ) ; Component replaced = put ( child ) ; child . setFlag ( FLAG_REMOVED_FROM_PARENT , false ) ; if ( replaced != null ) { replaced . setFlag ( FLAG_REMOVED_FROM_PARENT , true ) ; removedComponent ( replaced ) ; child . markupIndex = replaced . markupIndex ; } return this ; } final void autoAdd ( final Component component ) { } public final boolean contains ( final Component component , final boolean recurse ) { } @ Override public final Component get ( final String path ) { } public String getMarkupType ( ) { } public void internalAdd ( final Component child ) { } @ Override public void internalAttach ( ) { } @ Override public void internalDetach ( ) { } public final Iterator < Component > iterator ( ) { } public final Iterator < Component > iterator ( Comparator < Component > comparator ) { } public void remove ( final Component component ) { } public final void remove ( final String id ) { } public final void removeAll ( ) { } public final void renderAssociatedMarkup ( final String openTagName , final String exceptionMessage ) { } @ Override @ SuppressWarnings ( "unchecked" ) public Component setModel ( final IModel < T > model ) { } public final int size ( ) { } @ Override public String toString ( ) { } @ Override public String toString ( final boolean detailed ) { } public final Object visitChildren ( final Class clazz , final IVisitor visitor ) { } public final Object visitChildren ( final IVisitor visitor ) { } @ Override protected final MarkupStream findMarkupStream ( ) { } public final MarkupStream getAssociatedMarkupStream ( final boolean throwException ) { } @ SuppressWarnings ( "unchecked" ) public MarkupResourceStreamLookupResult newMarkupResourceStream ( Class < ? extends MarkupContainer > containerClass ) { } public final MarkupStream getMarkupStream ( ) { } @ Override protected void onComponentTagBody ( final MarkupStream markupStream , final ComponentTag openTag ) { } @ Override protected void onRender ( final MarkupStream markupStream ) { } protected void renderAll ( final MarkupStream markupStream ) { } protected final void renderComponentTagBody ( final MarkupStream markupStream , final ComponentTag openTag ) { } @ Override protected final void setMarkupStream ( final MarkupStream markupStream ) { } final boolean hasAssociatedMarkup ( ) { } private final void addedComponent ( final Component component ) { } private final void children_add ( final Component child ) { } private final Component < ? > children_get ( int index ) { } private final Component children_get ( final String id ) { } private final int children_indexOf ( Component < ? > child ) { } private final Component children_remove ( Component < ? > component ) { } private final Component children_remove ( int index ) { } private final Component children_set ( int index , Component child ) { } private final int children_size ( ) { } private final Component put ( final Component < ? > child ) { } private final void removedComponent ( final Component < ? > component ) { } private final void renderNext ( final MarkupStream markupStream ) { } public boolean isTransparentResolver ( ) { } }

Fix:
MarkupContainer . log . debug ( ( ( ( ( ( "Add<seq2seq4repair_space>" + ( child . getId ( ) ) ) + "<seq2seq4repair_space>to<seq2seq4repair_space>component<seq2seq4repair_space>" ) + ( this . getClass ( ) . getName ( ) ) ) + "<seq2seq4repair_space>with<seq2seq4repair_space>path<seq2seq4repair_space>" ) + ( MarkupContainer . getPath ( ) ) ) ) ;